Corrosion inhibition



Patented Apr. 11, 1944 oormosrou mnmrrron Hans 'C. Duus, Wilmington,DeL, assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., acorporation of Delaware No Drawing. Application November 12, 1941,Serial No. 418,699

20 Claims.

This invention relates to the prevention of corrosion and moreparticularly to prevention of corrosion in presence of alcohols andalcohol containing antifreeze compositions.

Many different substances have previously been proposed for use asfreezing point depressants in cooling fluids and among such suggestedmaterials various monoand polyhydric alcohols, alone or in combination,have been widely accepted,

In the use of such different freezing point depressants, particularly inconnection with the cooling systems of internal combustion engines,various problems of corrosion have developed due, primarily, to the widevariety .of metals and alloys with which water and the antifreezeliquids come in contact and against which metals there are exertedvarying degrees of corrosion. Consequently,.along with suggestions foruse of such different freezing point depressants, there have beenrecommendations for employing as many, if not a greater number of,substances which are active for inhibiting corrosion of metals withwhich the water and freezing point depressants come in contact. 7

The practical disadvantages of prior corrosion inhibitors have been highcost or slight efllciency or both. Furthermore, the majority ofpreviously proposed corrosion inhibitors have had little or no effectupon the corrosion caused by the alcohols upon the inner walls of thecontainers in which antifreeze liquids are normally packaged and stored.

It is an object of this invention to provide a new and improved class ofcorrosion inhibitors for use with alcoholic antifreeze materials. Other1 objects and advantages of this invention will be or comprise thecontainers within which such antifreeze liquids are normally packagedand stored. For example, in the use of teme-plated cans, particularlywhen the plated surfaces thereof are in contact with glycol orglycol-containing solutions, no staining or corrosion of the surfaces isapparent when the inhibitors of this invention are present and dilutionof the glycol with water causes no formation of undesirable whiteprecipi ing to this invention, by adding to monohydric or polyhydricalcohols such as methanol, ethanol,

ethylene glycol, propylene glycol, or the like, relatively smallquantities of a carbonate having the formula XRCOa, in which Xrepresents an alkali metal and R represents an alkyl or hydroxy alkylradical such as CHzCHzOI-I (the hydroxy alkyl radical of ethyleneglycol) or CHzCHOHCHzOH (the hydroxy alkyl radical of glycerine). Thus,according to the present invention, I have found that the corrosiveeffect of monoor polyhydric alcohols may be avoided by the additionthereto of from 0.01 to 5% by weight, based upon the alcohol, of suchspecific carbonates as sodium or potassium alkyl carbonates or sodium orpotassium glycol carbonates.

Althoughlarger and smaller quantities may be used effectively, if--desired, I have found that 0.2 to 2.0% of the carbonate, based uponthe weight of the alcohol, is preferred, with 0.2 to 1.0% being usuallysufiicient, to inhibit attack by the alcohol upon metals such as iron,copper, brass, solder and tin which are found in the metal parts ofcooling systems of internal combustion engines or in the containerswithin which alcohols are normally packaged or stored.

The carbonates of the present invention may be added to the alcohol inany manner desired, such as by first mixing with a small quantity ofalcohol, in order to obtain a homogeneous alcohol-carbonate solution,and the carbonate-containing alcohol thereafter mixed with largerquantities of alcohol or, alternatively, the carbonate may be produceddirectly in the main body of alcohol which is to be treated. If thelatter procedure is preferred, it may be accomplished by adding thedesired amount of an alkali metal hydroxide to the alcohol to be treatedand thereafter bubbling carbon dioxide through the resulting mixtureuntil neutrality is reached as shown by phenolphthalein.

As an example, 0.4 gram of alkali metal hydroxide may be added to eachcc. of alcohol and thereafter carbon dioxide bubbled therethrough untilneutrality is reached. In such a case approximately 0.44 gram of carbondioxide will be added per 0.4 gram of alkali metal hydroxide.

Various changes may be made in the methods and preferred embodiments ofthis invention without departing therefrom or sacrificing any of theadvantages thereof.

to 2.0% of a carbonate having the general formula RG03, in which Xrepresents an alkali metal and R represents a radical selected from thegroup consisting of alkyl and hydroxy alkyl radicals.

3. A method for inhibiting corrosion of metals in contact with normallyliquid aliphatic alcohols which comprises incorporating in the alcohol,based upon the weight of the alcohol, from 0.01 to of sodium methylcarbonate.

4. A method for inhibiting corrosion of metals in contact with normallyliquid aliphatic alcohols which comprises incorporating in the alcohol,based upon the weight of the alcohol, from 0.2 to 2% of sodium methylcarbonate.

5. A method for inhibiting corrosion of metals in contact with normallyliquid aliphatic alcohols which comprises incorporating in the alcohol,-

based upon the weight or the alcohol, from 0.01 to 5 of sodium glycolcarbonate.

6. A method for inhibiting corrosion of metals in contact withnormallyliquid aliphatic alcohols which comprises incorporating in the alcohol,based upon the weight of the alcohol, from 0.2 to 2% of sodium glycolcarbonate.

7. A method for inhibiting corrosion onmetals in contact with normallyliquid aliphatic alcohols which comprises adding to the alcohol from0.2% to 1.0%, based upon the weight of the alcohol, of an alkali metalhydroxide and thereafter passing carbon dioxide into the alcohol untilneutrality is reached.

8. A method for inhibiting corrosion of metals in contact with normallyliquid aliphatic alcohols which comprises adding to the alcohol from 0.2to 1.0%, based upon the weight of the alcohol, oi sodium hydroxide andthereafter passing carbon dioxide into the alcohol until neutrality isreached.

9. A method for inhibiting corrosion of metals in contact with methanolwhich comprises adding to the alcohol from 0.2 to 2% of an alkali metalalkyl carbonate.

10. A method for inhibiting corrosion of metals in contact with ethyleneg ycol which comprises incorporating in the glycol from 0.2 to 2% or analkali metal hydroxy alkyl carbonate.

11. A method for inhibiting corrosion of metals in contact with methanolwhich comprises adding to the alcohol from 0.2 to 2 of sodium methylcarbonate.

12. A method for inhibiting corrosion of metals in contact with ethyleneglycol which comprises incorporating in the glycol from 0.2 to 2% ofsodium glycol carbonate.

13. An antifreeze composition consisting substantially entirely of anormally liquid aliphatic alcohol containing from 0.01 to 5% of acarbonate having the general formula xacoa, in which X represents analkali metal and R represents a radical selected from the groupconsisting 01' alkyl and hydroxy alkyl radicals.

14. An antifreeze composition consisting substantially entirely of anormally liquid aliphatic alcohol containing from 0.2 to 2% of acarbonate having the general formula XRCOa, in which X represents analkali metal and R represents a radical selected from the groupconsisting of alkyland hydroxy alkyl radicals.

15. .An antifreeze composition consisting substantially entirely ofmethanol containing from 0.01 to 5% of an alkali metal alkyl carbonate.

16. An antifreeze composition consisting substantially entirely ofmethanol containing from 0.01 to 5% of an alkali metal methyl carbonate.

17. An antifreeze composition consisting substantially entirely ormethanol containing from 0.01 to 5% of sodium methyl carbonate.

18. An antifreeze composition consisting substantially entirely ofethylene glycol and from 0.01 to 5% of an alkali metal hydroxy alkylcarbonate.

19. An'antifreeze composition consisting substantially entirely ofethylene glycol and from 0.01 to 5% of an alkali metal glycol carbonate.

20. An antifreeze composition consisting substantially entirely ofethylene, glycol and from 0.01 to 5% of sodium glycol carbonate.

HANS C. DUUS.

